Added support for buildpack to work on a windows stack

[dbathgate]

Desired Outcome

This change is to add windows compatibility for the conjur buildpack.

Implemented Changes

Describe how the desired outcome above has been achieved with this PR. In
particular, consider:

• Added supply.bat/supply.ps1 windows scripts that ports the functionality of the supply bash script
• Added 0001_retrieve-secrets.bat windows batch script that ports the functionality of the 0001_retrieve-secrets.sh bash script
• Updated build step to compile a windows binary for conjur-env
• Added necessary buildpack files to manifest.yml

Connected Issue/Story

Resolves #[182]

CyberArk internal issue ID: [insert issue ID]

Definition of Done

At least 1 todo must be completed in the sections below for the PR to be
merged.

Changelog

• The CHANGELOG has been updated, or
• This PR does not include user-facing changes and doesn't require a
  CHANGELOG update

Test coverage

• This PR includes new unit and integration tests to go with the code
  changes, or
• The changes in this PR do not require tests

Documentation

• Docs (e.g. READMEs) were updated in this PR
• A follow-up issue to update official docs has been filed here: [insert issue ID]
• This PR does not require updating any documentation

Behavior

• This PR changes product behavior and has been reviewed by a PO, or
• These changes are part of a larger initiative that will be reviewed later, or
• No behavior was changed with this PR

Security

• Security architect has reviewed the changes in this PR,
• These changes are part of a larger initiative with a separate security review, or
• There are no security aspects to these changes

[szh]

Can you please signoff on your commits?

[szh]

It's looking like we won't be able to get Windows support in our CI environment so quickly, and we don't want that to hold up merging this. We're going to need to arrange for the Windows tests to run locally only, and document how to run them in CONTRIBUTING.md.

[szh]

I just rebased on main

[szh]

I've squashed the PR into a single commit

[szh]

LGTM, ready to merge!